5G is one of the most talked-about topics in the mobile communications industry and it totally deserves it. However, when a topic becomes so popular, lots of people say lots of things which makes it hard to separate the hype from reality. In this article, we will try our level best to take a more objective approach to explain 5G.
5G stands for the fifth generation of mobile networks where 5 stands for fifth and G stands for Generation. It is a successor of 4G, 3G, 2G and 1G mobile networks. 5G is based on a technology called New Radio (NR) just like 4G is based on LTE.
How is 5G different from earlier cellular technologies?
The concept of 5G is fundamentally different from earlier mobile technologies like GSM, UMTS, LTE etc. The earlier technologies were mostly about data speeds; so for example, HSPA+ could offer peak download speeds of up to 42 Mbps which increased considerably with LTE and later updates. 5G is not all about speed; it can definitely provide ultra-high data speeds, but it is a technology with the aim to revolutionise industries and not just consumer lives. The real promise of 5G, arguably, is that it is has a very quick response time and it is capable of supporting a large number of low-powered devices that can help digitise many industries.
Many use cases for 5G are very futuristic and it may take a good few years of development for those use cases to even become more widely known. The real demand for 5G networks will evolve over time as we become more and more digital. The lower latency of 5G coupled with its capability to support a vast number of devices makes it ideal for many market verticals including the manufacturing sector.
5G can operate in multiple frequency bands, which allows it to achieve a latency of 1millisecond or even lower when higher frequency bands are used. The lower latency of 5G networks makes them ideal for providing communications for self-driving cars, manufacturing, virtual reality (VR) and other IoT (Internet of Things) services.
For the general public in the short-term, 5G may be more about ultra-fast mobile broadband also known as Enhanced Mobile Broadband (eMBB). The challenge, in the short-term, maybe the lack of coverage in many areas which may take some time to overcome. The good news, however, is that 4G and 5G will co-exist for a very long time and when unlimited data packages become more common, it will only make things better for the customers.
How fast is 5G?
Under ideal network conditions, 5G can offer peak downlink speeds of over 10 Gbps with a latency of as low as 1 millisecond. As the downlink helps with the downloads, the download speed of anything around 10 Gbps or even 1 Gbps sounds amazing. A download speed of even 100-150 Mbps is exciting enough for most fibre broadband providers in the UK, so you can imagine what anything with Gbps in it means considering 1 Gbps equals 1000 Mbps. In real life though, we never really get to witness the peak speeds as a mobile cell serving us is usually serving lots of other people at the same time. The available network capacity and the resulting speeds get shared with many other mobile users and the data speeds we get on our mobile phones are the average speeds.
Just to give you an example of average speeds, we were able to test the 5G speeds of one of the key mobile operators in the UK back in November 2019. Now just remember that this was right after the initial 5G launch and it may be that the operator was using frequency bands with lower bandwidth. The two tests we did, gave us download speeds of 156.7 Mbps and 174.8 Mbps, and latencies of 2 milliseconds and 1 millisecond. The upload speeds that we got were not very different from what we usually get with 4G.
How does it work?
5G networks can operate in various frequency bands starting from below 1GHz and going all the way up to 28 GHz:
- Low band: Below 1GHz e.g. 700 MHz.
- Mid band: 1 to 6GHz e.g. 3GHz.
- High or Millimetre band: Over 6GHz especially 24-30 GHz.
According to the laws of physics, the wireless signals that have higher frequencies experience higher losses as they travel which means they offer limited coverage. In comparison, the signals that use lower frequencies can travel much further due to experiencing lower losses. Higher frequencies are however more suitable for improved (reduced) latency and higher throughput. Therefore, in 5G, lower frequency bands can be used for providing wide-area nationwide coverage. The higher frequency bands can provide more targetted coverage in smaller areas with low latency and high throughput. Lower frequency bands are also useful for services where always connected low-powered devices are needed. The lower frequency band for wide-area 5G coverage in Europe is the 700 MHz band. The equivalent in the US is the 600 MHz band.
FDD or TDD?
In all earlier mobile technologies including 4G LTE, 3G UMTS and 2G GSM, Frequency Division Duplex (FDD) has been the primary (or only) technique for uplink and downlink. Basically, FDD uses two separate frequency bands; one for the uplink and one for the downlink. 5G uses a slightly different approach. In 5G, the millimetre frequency band can use Time Division Duplex (TDD) where the same frequency band is used for uplink and downlink but the transmission is separated by different timeslots. The lower frequency bands (low and mid) may still use FDD.
Since higher frequency bands (mid and millimetre bands) offer limited coverage, they need to operate in a small-cell architecture for situations that require targetted coverage. Examples of that can include urban areas, office buildings, and manufacturing facilities etc. However, the wider coverage will need to be provided through the larger cells (macrocells) on lower frequency bands that can travel further. But that doesn’t mean that macrocells can’t use higher frequencies. Thanks to the beamforming technology that 5G employs, the wireless signal travels to the receiver in a more targetted way with more energy. Since higher frequencies offer higher antenna gains, they also form higher beams which can lead to extended coverage.
5G also enables network slicing which allows mobile operators to offer “virtual” sub-networks. It means they can create individual network slices for specific market verticals (sectors). For example, they can create a very targetted network slice using the millimetre band to achieve ultra-low latency for a manufacturing unit, but they can create another slice for the rest of the population in the same area for general 5G mobile coverage.
Access technique and channel bandwidth
5G uses OFDM (Orthogonal Frequency Division Multiplexing) which is the same access technology that LTE uses for the air interface (radio network). In 4G LTE, the sub-channel spacing is 15 kHz but 5G NR is more flexible and can use sub-carrier spacing in the multiples of 15 kHz e.g. 30 kHz, 60 kHz etc. From a bandwidth perspective, LTE uses a maximum carrier bandwidth of 20 MHz and by using multiple-carriers, it can use up to 5 carriers to achieve a maximum bandwidth of 20 MHz x 5 = 100 MHz.
In 5G NR, the maximum channel bandwidth is 400 MHz and with multiple-carriers, 5G can use up to 16 carriers which allows the maximum bandwidth to be 400 MHz x 16 = 6400 MHz or 6.4 GHz. Higher bandwidth leads to higher data speeds so as you can observe 5G can lead to much higher speeds as compared to LTE.